Various pharmaceutical products are designed for topical application, for instance in the form of gels, creams and lotions. Among such products are compositions including anti-acne actives, antimicrobial and antifungal actives, anti-wrinkle and anti-skin atrophy actives, skin barrier repair aids, cosmetic soothing aids, artificial tanning agents and accelerators, skin lightening actives, sunscreen actives, skin tightening agents, anti-itch agents, hair growth inhibitors, desquamating agents, antiglycation agents, wound healing actives, actives to treat psoriasis, skin cancer, impetigo, herpes, chickenpox and dermatitis and mixtures thereof.
Some of the above compositions include components that are insoluble or only slightly soluble in water, but are readily soluble in non-polar substances such as organic solvents and oils. However, compositions including oils and the like have certain drawbacks in their use. For example, they may produce a sticky and/or greasy feel upon application to the skin. The compositions may also be inconvenient for use by, for example, requiring an extended drying time after application to the skin and/or staining the skin and/or clothing. In addition, these compositions do not necessarily provide for a film layer that will be effective to retain volatile actives. Further, after application the compositions typically are easily solubilized by aqueous solutions such as perspiration which may lead to loss of the composition and/or the actives. Further, water or oil containing compositions often include emulsifiers which can cause skin irritation. In addition, the process of making these compositions typically involves heating which may lead to the loss of the actives by, for example, evaporation and/or sublimation.
Two classes of pharmaceutical compositions particularly prone to the aforementioned drawbacks are skin-care compositions and analgesics.
Of special interest in the category of skin care compositions are compositions including anti-wrinkle components, anti-skin atrophy components, skin repair components and mixtures thereof, and particularly skin care compositions selected from the group consisting of retinoic acid, retinoic acid derivatives, retinal, retinol, retinyl esters and mixtures thereof.
Retinol, perhaps the most well known of these compositions, is frequently used in anti-aging creams, lotions, and serums. Because retinol is very unstable to heat, light, and oxygen, products containing retinol currently must be manufactured under inert gas conditions and packaged in aluminum tubes to prevent oxygen or light from degrading the active retinol. These restrictive manufacturing and packaging conditions increase the overall cost of the skin-care products, making them unaffordable to many consumers.
Also of interest are analgesic compositions, particularly compositions selected from the group consisting of methyl salicylate, camphor, menthol and capsaicin. Methyl salicylate is a 2-hydroxybenzoic acid methyl ester which can occur naturally in wintergreen oil, betula oil, sweet birch oil, teaberry oil and in the leaves of Gualtheria procumbens L. Ericadeae and in the bark of Betula lenta L. Betulaceae. It can also be prepared by etherification of salicylic acid with methanol. Camphor is 1,7,7-trimethylbicyclo[2,2,1]heptan-2-one and occurs in all parts of the camphor tree, Cinnamomum camphora T. It is also synthesized from vinyl chloride and cyclopentadiene. Menthol, or 5-methyl-2-[1-methylethyl]-cyclohexanol, can be obtained from mint oils, for example, peppermint oil. It can also be obtained through hydrogenation of thymol. Capsaicin, or N-(4-hydroxy-3-methoxybenzyl)-8-methylnontrans-6-enamide, can be obtained from the fruits of plants of the Capsicum genus.
Water and oil containing compositions such as gels, lotions and creams are useful for application of menthol, camphor, and capsaicin and methyl salicylate as well as other analgesics. U.S. Pat. No. 5,124,320 and U.S. Pat. No. 5,013,726 disclose compositions in which methyl salicylate, menthol and camphor are dissolved into C12-C15 alcohols benzoate, eucalyptus oil and jojoba oil.
There remains a need for topically applied compositions which may be used to apply skin-care products. and/or analgesics which are easily and economically prepared, are non-sticky, greaseless, require less drying time after application to the skin, do not stain the skin, provide water resistance or waterproofing, act to efficiently retain actives and are not irritating to the skin.
In addition, a need exists for skin-care products, particularly retinol-containing skin-care products, which can be economically packaged in opaque containers and which remain stable when exposed to oxygen and/or higher than normal temperatures.